Al-Bara bin Azib (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "No one should slaughter the sacrifice before praying." My maternal uncle said: "O Messenger of Allah! On this day there is a great deal of meat; I slaughtered early to feed my family and neighbours. I have a young female goat (jadh'ah) that is better than a goat for meat; shall I slaughter it?" He said: "Slaughter it, but after you a jadh'ah will not suffice for anyone. This is the better of your sacrifices."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19113